Born at Genazzano in the Campagna di Roma, 1368; died at Rome, 20 Feb., 1431. He studied at the University of Perugia, became prothonotary Apostolic under Urban VI, papal auditor and nuncio at various Italian courts under Boniface IX, and was administrator of the Diocese of Palestrina from 15 December 1401, to 1405, and from 18 to 23 September, 1412. On 12 June, 1402 he was made Cardinal Deacon of San Giorgio in Velabro. He deserted the lawful pope, Gregory XII, was present at the council of Pisa, and took part in the election of the antipopes Alexander V and John XXIII. At the Council of Constance he was, after a conclave of three days, unanimously elected pope on on 11 November, 1417 by the representatives of the five nations (Germany, France, Italy, Spain and England) and took the name Martin V in honor of the saint of Tours whose feast fell on the day of his election. Being then only sub deacon, he was ordained deacon on 12, and priest on 13, and was consecrated bishop on 14 November. On 21 November he was crowned pope in the great court of the episcopal palace of Constance. (Concerning his further activity at the council see COUNCIL OF CONSTANCE.)

The influential family of the Colonnas had already given twenty-seven cardinals to the church, but Martin V was the first to ascend the papal throne. He was in the full vigor of life being only forty-one years of age. Of simple and unassuming manners and stainless character, he possessed a great knowledge of canon law, was pledged to no party, and had numerous other good qualities. He seemed the right man to rule the Church which had passed through the most critical period in its history - the so called Western Schism. The antipopes, John XXIII and Benedict XIII were still recalcitrant. The former, however, submitted to Martin at Florence on 23 June, 1419, and was made Dean of the Sacred College and Cardinal-Bishop of Frascati. The latter remained stubborn to the end, but had little following. His successor Clement VIII submitted to Martin V in 1429, while another successor to Benedict XIII, who had been elected by only one cardinal and styled himself Benedict XIV, was excommunicated by Martin V, and thereafter had only a few supporters. (see WESTERN SCHISM). On 22 April, 1418 Martin V dissolved the council but remained in Constance, concluding separate concordats with Germany (Mansi, "Sacrorun Conc. Nova et ampl. Coll" XXVII, 1189-93), France (ibid.,1184-9) England (ibid., 1193-5), Spain (Colecció completa de concordatos españ", Madrid, 1862, 9 sq.). A separate concordat was probably made also with Italy, though some believe it identical with the concordat with Spain. King Sigismund of Germany used every effort to induce Martin V to reside in a German city while France begged him to come to Avignon, but, rejecting all offers he set out for Rome on 16 May, 1418.

The sad state of Rome, however, made it impossible at that time to re-establish the papal throne there. The city was wellnigh in ruins, famine and sickness had decimated its inhabitants, and the few people that still lived there were on the verge of starvation. Martin V therefore, proceeded slowly on his way thither, stopping for some time at Berne, Geneva, Mantua and Florence. While sojourning in the two last-named cities, he gained the support of Queen Joanna of Naples, who was in possession of Rome and Naples, by consenting to recognize her as Queen of Naples, and to permit her coronation by Cardinal Legate Morosini on 28 October, 1419. She ordered her general Sforza Attendolo, to evacuate Rome on 6 March, 1419 and granted important fiefs in her kingdom to the pope's two brothers, Giordano and Lorenzo. With the help of the Florentines, Martin also came to an understanding with the famous condottiere Bracco di Montone, who had gained mastery over half of central Italy. The pope allowed him to retain Perugia, Assisi, Todi and Jesi as vicar of the church, whereupon Bracci restored all his other conquests, and in July 1420, compelled Bologna to submit to the pope.

Martin was now able to continue on his journey to Rome, where he arrived on 28 September, 1420. He at once set to work, establishing order and restoring the dilapidated churches, palaces, bridges, and other public structures. For this reconstruction he engaged some famous masters of the Tuscan school, and thus laid the foundation for the Roman Renaissance. When practically a new Rome had risen from the ruins of the old, the pope turned his attention to the rest of the Papal States, which during the schism had become an incoherent mass of independent cities and provinces. After the death of Braccio di Montone in June 1424, Perugia, Assisi, Todi and Jesi freely submitted to the papal territory. Bologna again revolted in 1428, but returned to the papal allegiance in the following year. In these activities, Martin V was greatly assisted by his kindred, the Colonna family, whom he overwhelmed with important civil and ecclesiastical offices. In his case, however, the charge of nepotism loses some of its odiousness, for, when, he came to Rome, he was a landless ruler and could look for support to no one except his relatives.

The tendency which some of the cardinals had manifested at the Council of Constance to substitute constitutional for monarchial government tin the Church and to make the pope subject to a General Council, was firmly and successfully opposed by Martin V. The council had decided that a new council should be convened every five years. Accordingly, Martin convened a council, which opened at Pavia in April 1423, but had to be transferred to Siena in June in consequence of the plague. He used the small attendance and the disagreement of the cardinals as a pretext to dissolve it again on 26 February, 1424, but agreed to summon a new council in Basel within seven years. He died, however, before this convened, though he had previously appointed Cardinal Giuliano Cesarini as president of the council with powers to transfer and, if necessary suspend it. Though Martin V allowed adjustment of the temporal affairs of the Church to draw his attention from the more important duty of reforming the papal court and the clergy, still the sorry condition of Rome and of the Papal States at his accession palliate this neglect. He did not entirely overlook the inner reform of the Church; especially during the early part of his pontificate, he made some attempts at reforming the clergy at St. Peter's and abolishing the most crying abuses of the Curia. In a Bull issued on 16, March 1425, he made some excellent provisions for a thorough reform but the Bull apparently remained a dead letter. (This Bull is printed in Dñ,"Beiträ sur politischen kirchlichen and Kulturgeschichte der sechs lletxten Jahrhunderte",II, Raisbon,1863, pp335-44.) He also opposed the secular encroachments upon the rights of the Church in France by issuing a Constitution (13 April 142), which greatly limited the Gallican liberties in that part of France which was subject to King Henry VI of England, and by entering a new concordat with King Charles VII of France in August, 1426 ( see Valois,"Concordats anté a celui de François I, Pontificat de Martin V" in "Revue des questions historiques", LXXVII, Paris, 1905, pp.376-427). Against the Hussites in Bohemia he ordered a crusade, and negotiated with Constantinople in behalf of a reunion of the Greek with the Latin Church. His bulls, diplomas, letters, etc. are printed in Mansai, "Sacrorum Conc. Et amp., Coll.," XXVII-XXVIII.